Art of cracking mineral oils



May 25, 1937. c. B. FORWARD ART OF CRACKING MINERAL OILS Filed June 29, 1954 2 Sheets-Sheet l l Ill. IIII-Irll //v ENTOR CHAUNCEY B. FORWARD,DECEASED BY LAURA w. FORWARD, EXECUTRlX Z; ATTORNEY May 25, 1937. c. a' FORWARD ART OF CRACKING MINERAL OILS Filed June 29, 1934 2 Sheets-Sheet 2 mmmmmmmml mmmm I III I U mm wwwwwwmww l l mu Sm MN Q n u l u um ml l wn lm H U mNk MN Rm Qm' x mm mm EC mm D: Y R D1 E m? m 0 N A A W m WRR mm B H CA I R M w A Patented May 25 1937 UNITED STATES PATENT @FFICE ART OF CRACKING MINERAL OILS Application June 29, 1934, Serial No. 732,966

9 Claims.

This invention relates to improvements in the art of cracking hydrocarbon oils for the production of more desirable hydrocarbon compounds of both lower and higher boiling point ranges. The invention comprises an improved process which is of especial value and application in the production of distillates suitable for use as motor fuels in internal combustion engines, from petroleum oils and fractions thereof. This application, as to common subject-matter, is a continuation in part of pending application Serial No. 235,206, filed November 2.3, 1927 which has matured into Patent No. 2,007,081 of July 2, 1935, which is in turn a continuation in part of copending applications Serial Nos. 318,484, 665,537 and 682,477, filed August 19, 1919, September 29, 192.3 and December 24, 1923 respectively.

It has been known that cracked distillates obtained by cracking special fractions derived from certain naphthenic and asphalt base crude oils detonate much less readily than straight run gasolines. It is also known that in exceptionally high temperature cracking operations such as those carried out in connection with the manufacture of gas for illuminating purposes, a low percentage of the stock charged may be obtained as a by-product distillate or condensate having good detonation inhibiting characteristics, but such distillates or condensates have the disadvantage of ordinarily containing a relatively high percent- 4 age of unsaturated compounds which decompose readily with the formation of gum which it is practically impossible to remove without excessive loss of the more stable unsaturated compounds. Such distillates also have a very offensive odor. Further, the major portion of the charging stock is converted into a permanent gas and only a relatively small yield of a condensate boiling within the range of present day internal combustion engine motor fuel specifications is obtained from cracking operations of this variety. The reactions incident to such operations are also accompanied by excessive formation of coke and carbon-like materials.

It has been universally assumed by petroleum refiners, petroleum chemists and even organic chemists as a group, that vapor phase cracking of petroleum hydrocarbons at high temperature is invariably accompanied by the formation of coke. 'This assumption has apparentlybeencorroborated by the fact that all of the very high temperature vapor phase cracking processes heretofore developed, as far as known, have been accompanied by excessive coke formation and the difficulties incident to this formation of coke and carbon-like materials have constituted a serious engineering problem and frequently resulted in disaster. Repeated operations have shown that this coke formation is unnecessary in the vapor phase cracking of petroleum oils even when very high temperatures are employed, and further that by vapor phase cracking at high temperature so conducted as to avoid coke formation, a distillate product is produced which is chemically quite diiierent from the distillate products of ordinary vapor phase cracking processes and which has desirable physical characteristics superior to any product now known.

The formation of these products is apparently due to the accurate control of the reactions taking place, hitherto unsuspected, which produced a product that is apparently never formed under the conditions existing in ordinary cracking processes.

Distillate products produced by the improved dom from gum-forming constituents in their crude state and without further treatment, and their superior ability to develop power when used as motor fuels in internal combustion engines, especially in engines having a high compression ratio.

The process of the invention is adapted to produce a high anti-knock distillate product from even the most refractory petroleum oils and distillates, including pure paraffin base oils from which the distillates obtained by ordinary cracking processes are notable for their detonation characteristics even at low pressures. This cracking process may be carried out with conversion of only a comparatively small percentage of the charging stock into fixed gas and with substantially no coke formation. For example, in the cracking of a purely parafi'in base gas oil by the improved process of the invention, a large yield of a distillate product has been produced which operates successfully as a motor fuel in an internal combustion engine having a comp-ression ratio greater than 11 to 1, without audible detonation, under conditions other than a change in compression ratio of the engine at which it was impossible to operate without audible detonation with a compression ratio greater than 4.3 to 1 when using a straight run Pennsylvania gasoline as the motor fuel, and at which it was impossible to operate without audible detonation with a compression ratio greater than 5.43 to 1 when using a blend of 50% pure benzol and 50% straight run Pennsylvania gasoline as the motor fuel. Further, when using samples of the improved distillate product as a motor fuel, the engine operated satisfactorily, though with regular detonation, when the compression ratio was increased to greater than 14 to 1.

According to the process of the invention, an advancing stream of the oil, preferably a gas oil or heavy naphtha distillate, is heated, vaporized and the generated vapors superheated to a temperature substantially in excess of their boiling point at the pressure employed so that the major part of the cracking reaction takes place in the vapor phase. The superheated oil vapors are then subjected to a digesting operation for a con.- siderable period of time at a uniform and accurately controlled temperature during which heat is supplied to the vapors at substantially the rate at which heat is absorbed in the reactions tali'ng place. As the high temperature products advance through the tubes of the digestion zone the reactions taking place gradually require less outside heat because of the heat added by exothermic reactions. The digesting operation is preferably continued until the exothermic reactions predominate over endothermic reactions, resulting in a product high in aromatic compounds. I

The stream of oil or vapors during the heating operation and during the digesting treatment above referred to is maintained in motion at a relatively high velocity and is heated for example by heat transfer from a heating medium positively circulated in indirect heat exchanging relation therewith. If the treatment in the digestion tubes is incomplete the cracked vapors may advantageously be subjected to a further digest.- ing treatment in an enlarged heat insulated zone during which no heat is supplied from an external source, but the, vapors are maintained above their cracking temperature by their own heat. In this further digesting treatment a polymerizing exothermic reaction continues by which heat is released and the temperature may rise without the external application of heat. An additional amount of conversion takes place during the last named digesting operation.

The cracked vapors from the digesting operation are preferably suddenly chilled from at or above the cracking temperature to below the cracking temperature, for example, by injecting a cooling medium, such as water or a relatively cool liquid hydrocarbon into the vapor stream at the point of discharge from the digesting zone. The injection of a cooling liquid into the vapors discharged from the digesting operation before their temperature has been materially reduced serves to prevent the formation of coke in any subsequent part of the system in such a manner as to foul the apparatus. Water may advantageously-be employed as the cooling medium because of its high latent heat.

The entire charge of cracked vapors may be condensed to form a single overhead distillate and any desired fraction separated therefrom by subsequent redistillation, or the vapor stream may be chilled from at or above the cracking temperature to below the cracking temperature, but not to below the condensing point of the major portion of the cracked vapors, and the vapors remaining uncondensed subsequently iractionally condensed in. a suitable dephlegmator to secure any desired end boiling point distillate without redistillation. The fresh oil supplied to the cracking zone may be preheated by heat exchange with the hot vapors and the cooling action of the fresh oil utilized to efiect partial condensation of the vapors. The pressure maintained on the vapors during the cracking treatment will vary with the character of the oil used as charging stock. For example, the digesting operation may be carried out under substantially atmospheric pressure and the oil supplied to the heating coils at the pressure necessary to maintain the desired rate of fiow therethrough. Or a pressure in excess of 2-50 pounds per square inch may be maintained on the vapors in the enlarged digesting zone and the oil supplied to the heating coil at a pressure of from about 400 to 600 pounds per square inch or higher. In general, the higher the pressure employed the greater will be the yield and the higher the quality of hydrocarbon constituents obtained which are of value as detonation inhibitors.

The process of the invention will be further described in connection with the accompanying drawings which illustrate in. a diagrammatic manner one form of apparatus adapted to carry out the process of the invention, but it is intended Fig. l is a diagrammatic representation in elevation and partly in section of one form of apparatus adapted to carry out the process of the invention.

Fig. 2 is a diagrammatic representation in elevation of a modification of the type of apparatus illustrated in Fig. 1.

An apparatus suitable for carrying out the process of the present invention is shown in Fig. 1 of the drawings in which the oil to be cracked is introduced into the system from storage through a pipe 2, and forced by means of a pump 4 and a pipe 6 through a preheating coil 2 mounted in the upper part of a fractionating tower l. The preheated oil from the coil 8 is conducted through a pipe E2 to a series of tube banks or sections M to 23 mounted respectively in insulated' heating chambers 24 to 33. The oil is heated to a cracking temperature in passing through these series of coils i l to 23, and then conducted through a valved transfer line 3 5 into the base of an enlarged cracking reaction and carbon settling chamber 35. Any carbon settled out in this chamber may be removed therefrom through valved outlet 35. Vapors are conducted from the chamber 35 through vapor line 33 and passed into a chilling nozzle it wherein a cooling fluid such as water is introduced into the vapors to reduce their temperature. Water or other cooling fluid is withdrawn from storage through a line 32 and forced by means of pump M and pipe it into the stream of vapors in the injector nozzle ie. The mixture of vapors and cooling fluid from the injector M! are conducted through a valved vapor line 48 into a chamber 5!] in the base of tower Any liquid material present in the mixture introduced into chamber 59 is separated out and withdrawn from the tower through a valved line 52, while the vapors are conducted through a vapor outlet 54 into the fractionating part of tower l. Low boiling point vapors are withdrawn from the upper part of tower ID through a valved outlet line 56 and conducted to a condenser 58 where the readily condensible materials are condensed. Condensate from condenser 58, together with uncondensed gases are conducted through a line 60 into a receiver 62 from which gases are removed through a valved line 64 and distillate through a valved line 66. Heavy reflux condensate is withdrawn from the fractionating section of tower Ill through a valved line 61 for return to the cracking operation or to storage.

The series of pipe coil sections 14 to 23 mounted in chambers 24 to 33 form a continuous long coil which serves for the heating and cracking of the oil. In one installation in which this apparatus was used for cracking oil the heating chambers 2 3 to 32 were about 12 inches in diameter and 18 feet long and the coil in each chamber was built of inch pipe connected with return bends to form coils of from 500 to 600 feet in length. In this installation the chamber 33 was 24 inches in diameter and 18 feet long and the coil 23 therein was made up of one inch pipe connected by return bends. This coil 23 was approximately 2300 feet in length. The latter portion of the continuous coil formed by the coil sections Hi to 23 may advantageously be of a slightly greater diameter than the initial portion for the purpose of decreasing the resistance to flow due to'the expansion and increase in volume of the oil constituents passing therethrough.

In the installation referred to above, the enlarged reaction chamber 35 was approximately 3 feet in diameter and 23 feet high. This chamber was heavily insulated to prevent loss of heat.

In the operation of the apparatus above described the coil sections mounted in heating chambers 24 to 33 were heated with superheated steam. This steam was produced by conducting water from any suitable storage or source through a pipe 68 and forcing it under pressure by means of a pump Ill through a pipe line 72 into a combined boiler and superheater coil 14 mounted in a furnace 16. The water passing into this coil is vaporized and superheated during its passage therethrough to a temperature of l100-1400 F. but is preferably in the neighborhood of 1200 F. This high temperature steam is conducted through a transfer line 18 into a header 8!] which serves to supply superheated steam directly to heating chambers 28 to 33 by means of valved connecting pipes 82. Each of the chambers 21 to 33 are provided with valved steam discharge lines 84 and these lines from chambers 29 to 33 discharge into a header 86. The superheated steam somewhat reduced in temperature as discharged from chambers 29 to 33 into header 86, is conducted through a connecting line 88 into heating chamber 21. The steam discharged from chambers 21 and 28 through lines 84, is conducted through a connecting line 90 into heating chamber 26, and from there through a valved connecting line 92 into heating chamber 25. superheated steam at a substantially reduced temperature is discharged from chamber through a valved line 94 and conducted into the first heating chamber 24 in which the first coil 14 is mounted. Steam is discharged from chamber 24 through a line 96 into an insulated steam drum 98 from which the steam may be discharged through a valved line I02 to any suitable point, or may be reintroduced into the mid-portion of the coil 14 and reheated. If the steam is reheated, it will only be necessary to supply the necessary superheat.

The rate of heat transfer from the heating medium supplied to chambers 24 to 33 may be greatly increased by maintaining the highly heated gaseous heating medium at a relatively high pressure. superheated steam when used in the manner described above at a high pressure comprises a particularly advantageous heating medium because of its high specific heat. Various arrangements may be employed for compressing the steam withdrawn irom steam drum 9S, superheating it and reusing it in the heating chambers 24 to 33.

It is also apparent that other heating media may be used instead of steam, for example, nitrogen, carbon dioxide, or other gaseous substances, preferably inert, are suitable. Products of combustion are also a common and well-known heating medium for heating pipe stills for cracking and distilling oil.

In Fig. 2 of the drawings, the same reference characters are employed to describe the same or corresponding apparatus elements. It will be noted that substantially the only distinction between the apparatus shown in Figs. 1 and 2, is that the enlarged reaction chamber of Fig. 1 has been eliminated. In the apparatus as shown in Fig. 2, the highly heated oil products discharged from coil 23 are conducted through transfer line 34 directly into the mixing and quenching nozzle in which cooling medium is mixed with the high temperature oil constituents. The mixed products are then discharged through a line 48 into the chamber in the base of tower I 0.

In the operation of the apparatus illustrated in Fig. l, the fresh oil charging stock which is preferably a distillate oil is preheated in the coil 8 to a temperature of from 100 to 450 F. and then conducted into the first of the series of coil sections mounted in heaters 24 to 33. In the passage of the oil through coil sections M to II, it is heated to a temperature in the neighborhood of 850 F. and substantially all converted into vapors. If the charging stock is a topped crude or a fuel oil, a separator may be placed in the oil line between coils l1 and 18 to separate heavy residue from the vapors. The vapors pass on through the coils l8-23 and the residue would be removed from the separator. This separator is illustrated in Patent No. 1,698,811, granted January 15th, 1929. The vapor products in passing through the coil sections [8 to 23 are raised to a cracking temperature of from 950 to 1050 F. and maintained at that temperature during their passage through a substantial part of the coil. The oil constituents may be brought up to the de sired cracking temperature within this range by the time they reach the outlet of coil section 19 or at least by the time the outlet of coil section 22 is reached. The remaining length of coil through which the vapors pass after attaining the desired temperature should be so regulated as to subject the vapors to a substantial time reaction. It is apparent that the quicker the oil constituents passing through coil sections Hi to 23 are brought to the cracking temperature, the greater the length of time the oil constituents can be maintained at the cracking temperature in the resired point in the coil, and thereafter maintain the temperature by supplying the proper quantity of high temperature steam to the various heating chambers. All of the steam used in heating chambers 28 to 33 is conducted to the preliminary heating chambers 24 to 21, with the exception that the steam from heating chamber 28 is not passed into chamber 21. This large volume of steam supplied to chambers 24 to El serves to quickly raise the oil from a temperature of about 400 F. to a temperature of about 850 F. The quantity of high temperature steam supplied to heatingchambers such as 33, in which the oil has already attained the cracking temperature need only be suiii'cient to provide for the ordinary heat losses and for any heat of reaction which may be necessary.

The length of coil necessary to effect the desired cracking reaction should be sufficient to carry the reaction beyond that required for maximum conversion, so that some polymerization and molecular rearrangement of the oil products occurs before they leave the coil 23. The temperature of the oil vapors within the coils 29-23 has been found to be very critical and a slight increase in the temperature of the heating medium in chambers 3l-33 causes substantial variations in the oil temperature at this point which also results in a marked variation in the character of the product obtained. This is apparently due to the prolonged digestion in the coil sections 2| to 23, wherein the usual endothermic conversion reaction has been carried to a point where exothermic polymerizing reactions are initiated. By carefully controlling the heat input in this critical range, it is possible to control the exothermic reaction which is allowed to take place. The temperature may be so adjusted that a part of the exothermic reaction may be allowed to proceed in the enlarged reaction chamber 35 after the oil constituents have been discharged from the heating coil section 23.

The character of the distillate therefore may be accurately controlled by regulating the temperature and the length of time which the oil vapors are maintained at the cracking temperature. It is apparent however that the character of the charging stock as well as the character of the desired distillate product will influence and govern the selection of the temperatures and pressures to be used, as well as the rate at which the oil will be charged to a given apparatus. The effects of varying the cracking temperature and the length of time which the oil constituents are maintained at the cracking temperature are best illustrated by specific examples of runs made under different operating conditions.

The enlarged reaction chamber 35 serves as a convenient means for increasing the time reaction and also provides a point for the separation of free carbon which forms, to a slight extent in the vapors being cracked. This carbon which is a finely divided dry powder, resembling carbon black does not exceed %th of 1% of the total oil charged. The carbon may be blown from the chamber 35 through the valved conduit 36 without interrupting the operation of the apparatus.

The temperature of the oil vapors in chamber 35 depends on the discharge temperature of the vapors leaving coil section 23, and it may vary from about 875 F. to 1050 F. In operating the apparatus so that the discharge temperature from the coil 23 is approximately 975 F. the average temperature in chamber 35 will be approximately 875 F. If the temperature of the oil leaving coil section 23 is raised to 985 F. the average temperature in chamber 35 will be approximately 940 F. In this case an increase of 10 F. in the discharge temperature from coil 23 results in an increase of 65 F. in the temperature of the oil vapors in chamber 35. The extent of the exothermic reaction desired in the chamber 35 may therefore be accurately controlled by regulating the temperature of the vapors leaving coil section 23. If an extremely high anti-knock motor fuel product is desired, this may be obtained by controlling the temperature so that it does not rise substantially above 1950" F. in chamber 35. Higher temperatures have been found to be uneconomical in this type of process and to produce a large proportion of fixed gases.

The cracked vapors discharged from reaction chamber 35 through the line 38 are suddenly chilled to below their cracking temperature by injecting water or other suitable cooling fluid into the vapor stream at the point of discharge from the chamber, for example in the mixing nozzle 40. The introduction of a sumcient quantity of water to reduce the temperature of the oil vapors to about 700 F. has been found to satisfactorily prevent the formation of coke'in any part of the apparatus through which the vapors or condensates subsequently pass. The mixture of chilling medium and oil constituents is discharged through the line 38 into separating chamber 50 from which any high temperature residue may be withdrawn and the vapors conducted through the conduit 5i into the fractionating part of tower I0. The vapors are fractionated and treated in the usual manner in the 1 remaining parts of the apparatus.

The uncondensed vapors and gases discharged from receiver 62 through pipe 55 may be treated by absorption or compression for the recovery of readily condensable constituents suitable to comprise a part of the gasoline product.

The apparatus shown in Fig. 2 is intended to be operated in substantially the same manner as that shown in Fig. 1 except that the enlarged reaction chamber is entirely eliminated and the cracking reaction therefore is completed in the heated coil section 23 and any of the previous sections found to be necessary in order to give the proper time reaction. The apparatus of Fig. 2 which does not include the reaction chamber 35 may be operated in such a way as to very accurately control the cracking reaction. For example, the oil constituents may be brought to the desired cracking temperature at any point in the coil which includes sections it? to 23, so that the remaining part of the coil can be used for the purpose of carrying on the time reaction.

Each of the heating chambers 28 to 33 is pro vided with individual supply lines for heating medium for bringing about this result. -If an exothermic reaction is to be carried out in the coil section 23, it is apparent that very little high temperature steam will need to be supplied to chamber 33. The time for reaction in coils 3-23 is conveniently controlled by the velocity of circulation of the vapors.

The following examples are given to illustrate the flexibility of the operation of the cracking apparatus illustrated and described. The most advantageous method of operation will, of course, depend on the market demand, as the apparatus may be operated to produce distillates representing different quantities of the oil charged and having widely different physical characteristics. Of the following examples, the

run designated as Example 1 was carried out in an apparatus substantially similar to the installation above described, in which a coil approximately 350 feet in length was employed as the digesting coil 23, whereas in the other runs a much longer coil was substituted therefor. The coil used in the latter tests was approximately 2300 feet in length, and a comparison of two runs made with the diiferent equipment, but with substantially the same temperatures, pressures, and rate of throughput will clearly illustrate the fect of the length of time of exposure to high temperatures on the quantity and character of the distillates obtained.

In each of the following runs steam was supplied from the boiler and superheater coil M at a temperature of about 1150 to 1200 F. and fresh oil supplied to the system at a rate of about 180 gallons per hour.

The fresh oil charged was a 38 B. gas oil fraction from a Pennsylvania type crude oil. The boiler was operated so as to supply steam at a pressure of about 250 pounds per square inch and the steam receiver 08 maintained at a pressure of 225 pounds per square inch more or less as required to maintain the necessary flow of steam through the drums 33 to 2A. The vapors in the digesting chamber 35 were maintained at a pressure of about 225 pounds per square inch, under which conditions a pressure of about 400 to 450 pounds per square inch was required at the pump 4 to maintain a flow of 180 gallons per hour of fresh oil through the heating coils. After substantially constant operating conditions were established the average temperature of the steam in the drum 33 was held at about 15 to 30 F. higher than the average temperature of the oil Vapors in the heating coil 23.

Example N o. 1

Steam was circulated through drums at to 33 at a rate regulated to maintain the temperature of the oil vapors discharged from the coil 23 at approximately 975 F. The vapors discharged from the digesting chamber 35 were condensed to form a single crude distillate product, which represented approximately of the total oil charged, and had a gravity of 45 Be. Approximately 70% of the crude distillate was obtained as an overhead distillate by subsequent redistillation. The redistilled product had an end boiling point slightly below fl3'7 E, a gravity of 56 Be. and contained slightly in excess of 20% aromatic hydrocarbons.- In this operation the conditions were controlled so that the endothermic reaction was carried to completion and possibly a very small exothermic reaction was obtained. About 4% of the fresh oil charged to the system was recoverable from the uncondensed vapors as a light distillate.

' Example No. 2

This run was made using a digesting coil approximately sixtimes as long as the digesting coil employed in Example 1. The vapors discharged from the digesting chamber 35 were condensed as a single crude distillate product, having a gravity of 25 B., representing about 70% of the total oil charged. About 8% of the oil charged was recoverable from the uncondensed gases as a light distillate. The effect of the time of exposure to the high temperature maintained in the digesting coil due to the greater length of the coil will be evident from a comparison of the gravity of the product and the yield obtained in this example as compared with those obtained in the run given as Example No. 1, during which substantially the same temperatures were maintained although a much shorter digesting coil 23 was employed.

Example No. 3

Another run was made using the same apparatus as employed in the run given as Example No. 2. During this run steam was circulated through the drums 24 to 33 at a rate sufficient to maintain the temperature of the oil vapors discharged from the coil section 23 at a temperature of 1030 to 1040" F. The vapors discharged from the digesting chamber 35 were condensed as a single crude distillate product, having a gravity of 22 B., representing about 68.5% of the total oil charged. An analysis of the crude distillate showed it to contain 96% unsaturated and aromatic hydrocarbon compounds. On subsequent redistillation approximately 53% of the crude distillate product was obtained as an overhead distillate having a gravity of 3'7.5 B., and an end boiling point slightly below 437 F. In addition, about 10% of the total oil charged was recoverable from the uncondensed gases as a light distillate. In this operation, part of the exothermic reaction has been allowed to occur in the coil and an additional amount in the chamber 35.

Example No. 4

This run was made using the same digesting coil as in Examples 2 and 3. Steam was circulated through drums 24 to 33 at a rate sufficient to maintain the temperature of the oil vapors discharged from the coil section 23 at approximately 1050 F. The vapors discharged from the digesting chamber 35 were condensed to form a single crude distillate product having a gravity of about B., which represented approximately 65% of the total oil charged. On subsequent redistillation 50% of the crude distillate was obtained as an overhead distillate having a gravity of 328 B. and an end boiling point of approximately 437 F. About 12% of the fresh oil charged through the system was recoverable from the uncondensed gases as a light distillate. The redistilled product on analysis was found to contain 82.9% aromatic hydrocarbons, 17.1% other unsaturated hydrocarbons and no naphthene or paraffin hydrocarbons.

When a substantial exothermic reaction is produced in the operation, the temperature starts to rise without the external application of heat and the Beaum gravity of the crude distillate product decreases, the exact nature of the product being governed by the extent to which the polymerization reaction is allowed to proceed. There is apparently a limit to the extent to which the polymerization reaction can be carried at a given temperature due apparently to the formation of stable compounds. When operations are conducted so that the temperature of the vapors leaving the long digesting coil is above 1050 F., further digestion appears to result in partial decomposition of the stable compounds if the chamber 35 is used, with the formation of additional non-condensable gas and carbon.

Having thus described the invention in its preferred form, what is claimed as new is:

1. The process of producing a high anti-knock motor fuel product of the type of gasoline containing in excess of 75% aromatic hydrocarbons by cracking petroleum oil distillates of higher boiling point, which comprises passing the distillate to be cracked at a superatmospheric pressure of several hundred pounds per square inch continuously, uninterruptedly and without separation of any of its constituents in a confined rapidly flowing stream of restricted cross section and heating the distillate to a temperature of from 950 to 1050 F., heating and maintaining the stream of distillate at approximately its attained temperature for a substantial period of time sufficient to convert in excess of 40% of the oil of said stream per pass into lower boiling point products boiling within the gasoline range and for a time sufiicient to initiate and carry out a predominant exothermic reaction in the oil constituents, controlling the temperature of the oil stream during the continuance of said exothermic reaction so as to prevent a rise in tem perature above approximately 1050 F., thereafter discharging the highly heated products into an enlarged reaction chamber in which said exothermic reaction is permitted to continue entirely in the vapor phase, discharging the converted products from said enlarged chamber and cooling and fractionating the same to recover the desired motor fuel product containing in excess of 75% aromatic hydrocarbons.

2. The process of producing a high anti-knock motor fuel containing in excess of 50% aromatic hydrocarbons by cracking a higher boiling petroleum oil distillate, which comprises passing the distillate to be cracked at a pressure of at least 225 lbs. per square inch continuously, uninterruptedly and without separation of any of its constituents in a confined rapidly flowing stream of restricted cross section through a heating zone and heating the distillate therein to a temperature at which decomposition of the oil takes place, heating and maintaining the resulting products at substantially their attained temperature for a period of time sufficient to initiate and carry out an exothermic polymerizing reaction to form said aromatic compounds, said period of time approximating that required for an oil of approximately 38 B. gravity and at a temperature of from 850 to 975 F. to pass through a one inch coil about 2300 feet in length when supplied thereto at a rate of 180 liquid gallons per hour with an outlet pressure on the coil of 225 lbs. per square inch, controlling the temperature during said heating to prevent its rise above about 1050 F., discharging the re sulting products at the high temperature attained by the oil of said stream into an enlarged cracking zone in which the exothermic reaction is continued, and thereafter chilling and fractionating the resulting cracked products to secure the desired motor fuel.

3. The process of cracking hydrocarbon oils for the production of a high anti-knock motor fuel product containing in excess of 50% aromatic hydrocarbons, which comprises passing an oil distillate at a pressure of at least 400 lbs. per square inch continuously, uninterruptedly and without separation of the vapors in a confined stream of restricted cross section through a heating zone in which the oil is heated to a temperature of from 950 to 1050 F., maintaining the oil of said stream at said temperature for a substantial period of time during which a predominant exothermic cracking reaction is initiated and carried out in the oil constituents of said stream to convert a substantial proportion thereof into aromatic hydrocarbons, said period of time approximating that required for an oil of approximately 38 B. gravity and at a temperature of from 850 to 975 F. to pass through a one inch coilabout 2300 feet in length when supplied thereto at the rate of 180 liquid gallons per hour with an outlet pressure on the coil of 225 lbs. per square inch, controlling the temperature of the oil stream during the continuance of said exothermic reaction so as to prevent a rise of temperature to above approximately 1050 F., and thereafter cooling and fractionating the resulting cracked products to separate the desired motor fuel.

4. The process of producing a high anti-knock motor fuel containing in excess of 50% aromatic hydrocarbons by cracking the petroleum oil distillate, which comprises conducting the distillate in a confined stream of restricted cross section first through a zone in which the oil distillate is heated to a temperature sufiicient to effect a substantially rapid cracking of the oil, and then passing the resulting products uninterruptedly and without separation of any of their constituents as a continuation ofsaid stream through a zone in which the cracking temperature is maintained for a substantial period of time and in which an exothermic reaction is produced by the polymerization of the constituents of said stream, said period of time approximating that required for an oil of approximately 38 B. gravity and at a temperature of from 850 to 975 F. to pass through a one inch coil of about 2300 feet in length when supplied thereto at the rate of 180 liquid gallons per hour with an outlet pressure on the coil of 225 lbs. per square inch, maintaining a pressure of at least 225 lbs. per square inch in said second zone, controlling the temperature of the oil stream in the second zone to prevent its rise above about 1050 F., and thereafter cooling and fractionating the result ing products to separate the desired motor fuel containing in excess of 50% of aromatic hydrocarbons.

5. The process of cracking petroleum oils for the production of a high antiknock motor fuel product containing in excess of 50% aromatic hydrocarbons, which comprises passing the oil to be cracked through a heating zone and therein rapidly raising the temperature of the oil to a point at which a substantially rapid cracking of the oil takes place, passing all of the resulting oil constituents under a pressure of at least 225 pounds per square inch uninterruptedly r and without separation of any part of the oil constituents through a second heating zone in which the attained temperature is substantially maintained and in which a predominant exothermic polymerizing reaction is initiated and allowed to proceed for a sufficient time to produce said aromatic hydrocarbons, heating the oil in said second zone for a period of time approximating that required for an oil of approximately 38 B. gravity and at a temperature of from 850 to 975 F. to pass through a one inch coil about 2300 feet in length when supplied thereto at the rate of 180 liquid gallons per hour with an outlet pressure on the coil of 225 lbs. per square inch, controlling the temperature in said second zone to prevent its rise above about 1050 F., thereafter suddenly chilling the highly heated products to a temperature of approin'mately 700 F., and fractionating the resulting chilled products to separate the desired motor fuel.

6. The process defined by claim 5 in which the oil stream is maintained at approximately the attained cracking temperature in the second heating zone for a period of time sufiicient to convert in excess of 40% of the charging stock per pass into a motor fuel product boiling within the gasoline range of boiling points and containing in excess of 50% aromatic hydrocarbons.

7. The process of cracking petroleum oils for the production of a high anti-knock motor fuel product containing in excess of aromatic hydrocarbons, which comprises passing a paraifin base petroleum oil distillate at least as high boiling as a heavy naphtha in a long confined stream of restricted cross-section through a heating zone and therein rapidly raising the temperature of the oil stream to at least 850 F. at which a substantially rapid cracking of the oil takes place, continuously and uninterruptedly passing all of the constituents of the oil stream at a pressure of at least 225 pounds per square inch from said heating zone through a second long heating zone of restricted cross-section in which the stream of oil is heated and maintained at a temperature not in excess of about 1050 F., initiating and carrying out a predominant exothermic polymerizing reaction in said second zone to produce said aromatic hydrocarbons, maintaining the oil constituents in said second zone for a period of time equivalent to that required for -a gas oil of approximately 38 B. gravity and at a temperature of from 850 to 975 F. to pass through a one inch coil about 2300 feet in length when supplied thereto at the rate of 180 liquid gallons per hour with an outlet pressure on the coil of 225 pounds per square inch, controlling the temperature in the said second heating zone and thereafter cooling and fractionating the resulting products to separate the desired motor fuel.

8. The process of producing a high anti-knock motor fuel product of the type of gasoline containing in excess of 50% aromatic hydrocarbons by cracking petroleum oil distillates of higher boiling point, which comprises passing the distillate to be cracked at a superatmospheric pressure of several hundred pounds per square inch continuously, uninterruptedly and without separation of any of its constituents in a confined rapidly flowing stream of restricted cross section and heating the distillate to a temperature of from 950 to 1050 F., heating and maintaining the stream of distillate at approximately its attained temperature for a substantial period of time sufficient to convert in excess of 40% of the oil of said stream per pass into lower boiling point products boiling within the gasoline range and for a time sufficient to initiate and carry out a predominant exothermic reaction in the oil constituents, controlling the temperature of the oil stream during the continuance of said exothermic reaction so as to prevent a rise in temperature above approximately 1050 F., cooling the converted products of said stream and fractionating the same to recover the desired motor fuel product containing in excess of 50% aromatic hydrocarbons.

9. The process of producing a high anti-knock motor fuel containing in excess of 50% aromatic hydrocarbons by cracking a higher boiling petroleum oil distillate, which comprises passing the distillate to be cracked at a pressure of at least 225 lbs. per square inch continuously, uninterruptedly and without separation of any of its constituents in a confined rapidly flowing stream of restricted cross section through a heating zone in which the distillate is heated to a temperature at which decomposition of the oil takes place and an exothermic polymerizing reaction initiated, continuing the exothermic reaction by passing all of the products of said stream of restricted cross section as a continuation of said confined stream through a zone in which a sufiiciently high temperature is maintained to carry out said exothermic polymerizing reaction to thereby form said aromatic hydrocarbons, maintaining said distillate and the products produced therefrom at and above said decomposition temperature in said stream for a period of time approximating that required for an oil of approximately 38 B. gravity and at a temperature of from 850 to 975 F., to pass through a one inch coil about 2300 feet in length when supplied thereto at a rate of 180 liquid gallons per hour with an outlet pressure on the coil of 225 pounds per square inch, controlling the temperature during said heating to prevent its rise above about 1050 F., and thereafter cooling and fractionating the resulting cracked products of said stream to secure the desired niotor fuel.

LAURA W. FORWARD, Erecutrir of the Last Will and Testament of Chauncey B. Forward, Deceased. 

